World first culvert construction in the Manning Valley could save local government sector millions

Innovators: Carey Molloy of Matrix Thornton Consulting Engineers and Grant Calvin of MidCoast Council see the potential for waffle pod construction to assist councils in Australia with culvert engineering and cost challenges.

It’s a world first culvert construction method. It delivered dramatic savings to MidCoast Council’s budget and is the outcome of a collaboration with Oxley Island business, Matrix Thornton Consulting Engineers.

Drive on Belbora Creek Road, north off The Bucketts Way between Taree and Gloucester and you will cross a culvert. It's the first on the road and unremarkable in appearance to the untrained eye - it is only when you talk to Grant Calvin and Carey Molloy that you can see it represents an evolution in engineering - that it is a fusion of residential and bridge construction that could save the cash-strapped local government sector millions of dollars.

Grant Calvin is a senior survey designer with MidCoast Council and he is excited by the engineering innovation that cut the $400,000 budgeted cost of the works to $186,000. He recently advocated it to industry professionals at an Association of Public Authority Surveyors NSW conference and took out the coveted Keith Haddon Award for the paper. He wants other councils to know about the innovation and says “we’ve improved the level of service, done it in a sustainable way, it’s cost effective. Those are the catch phrases that are thrown around local government and we ticked them off.”

Construction: Residential concrete slabs are formed with waffle pods, however, in a world first solution, they were used to create a Belbora Creek Road culvert.

Budget constraints and a massive backlog of deteriorating infrastructure is a significant challenge for MidCoast Council. Belbora Creek Road has numerous culverts and most are located in the former Gloucester Shire Council region. It chose to tackle the task of upgrading its culverts in the early 1990’s and it meant they went under water only once or twice a year. In contrast, the culvert in the former Greater Taree area went under water with minimal rainfall. It was not an option to replicate the construction method of the other culverts, says Grant, as the cost of girder logs had increased from $500 to $5000 each. That’s when council asked Matrix Thornton Consulting Engineers to find a creative solution to the challenge.

Carey Molloy says the team came up with 20 different options but it was waffle pod technology developed for residential concrete house slabs that ticked the right boxes.

“It was bloody obvious really,” Carey said. “Waffle pods came out on top in the cost benefit analysis and we reuse them after you dig them out.”

Grant says the culvert also enables fish passage and maintains resident access to water, sharing that “if council had used the standard methodology to build it we would have lowered the water table down to the bed of the creek. It’s a win in so many ways.”

Completion: Better road access after rain, fish passage and continuing creek water access for residents are a few of the positive outcomes following the culvert upgrade.